The rapid discharge heating and forming (RDHF) method, as described in U.S. Patent Publication No. 2009/0236017, uses electrical current to heat a metallic glass charge substantially uniformly at time scales far shorter than typical times associated with crystallization, and shape the metallic glass into a metallic glass article. One example of a RDHF process is injection molding (as described in U.S. Patent Publication No. 2013/0025814, filed Jan. 31, 2013). Another example of a RDHF process is calendaring (as described in U.S. Pat. No. 8,613,815). In both methods, the metallic glass feedstock is rapidly and substantially uniformly heated by the electrical current flowing through it. In the injection molding method, the heated and softened feedstock is urged to flow into a mold. In the calendaring method, the heated and softened feedstock is urged to flow between a set of at least two rollers where it is shaped into a sheet. In both methods, the softened metallic glass is shaped and simultaneously cooled rapidly enough to form a metallic glass article.
In conventional RDHF methods, a feedstock barrel electrically insulates, mechanically supports, and confines the feedstock. Therefore, the feedstock barrel should exhibit low electrical conductivity and breakdown voltage together with high fracture toughness, thermal/chemical stability, and machinability/formability. Achieving electrical insulation together with mechanical performance is mutually exclusive in most typical engineering materials. For example, ceramics are very good electrical insulators but have poor mechanical performance, as they are generally brittle. On the other hand, metals are generally very tough, but they are poor electrical insulators as their electrical resistivities are generally very low.